Loss of Sister Kinetochore Co-orientation and Peri-centromeric Cohesin Protection after Meiosis I Depends on Cleavage of Centromeric REC8

Abstract

2 Summary Protection of peri-centromeric REC8 cohesin from separase and sister kinetochore attachment to microtubules emanating from the same spindle pole (co-orientation) ensure that sister chromatids remain associated after meiosis I. Both features are lost during meiosis II, when sister kinetochores bi-orient and lose peri-centromeric REC8 protection, resulting in sister chromatid disjunction and the production of haploid gametes. By transferring spindle-chromosome complexes (SCCs) between meiosis I and II cells, we have discovered that both sister kinetochore co-orientation and pericentromeric cohesin protection depend on the SCC and not the cytoplasm. Moreover, the catalytic activity of separase at meiosis I is necessary not only for converting kinetochores from a co-to a bi-oriented state but also for deprotection of pericentromeric cohesin and that cleavage of REC8 may be the key event. Crucially, we show that selective cleavage of REC8 in the vicinity of kinetochores is sufficient to destroy co-orientation in univalent chromosomes, albeit not in bivalents where resolution of chiasmata through cleavage of Rec8 along chromosome arms may also be required. 65the fission yeast S.pombe (Gregan et al., 2008) and indeed is absent from metazoan 66 genomes (Plowman et al., 2019), some other mechanism must confer co-orientation in 67 eukaryotes with regional centromeres. In fission yeast, a meiosis-specific version of 68 cohesin containing a Rec8 kleisin subunit is necessary to prevent bi-orientation during 69 meiosis I (Watanabe and Nurse, 1999; Sakuno et al, 2009). This suggests that cohesin 70 5 mediates co-orientation by holding sister centromeres together. Though plausible, this 71 hypothesis has never been rigorously proven. In an attempt to target specifically the 72 centromeric cohesin population for cleavage using fission yeast strains expressing a 73 CenpC-TEV fusion and Rec8 containing TEV sites, there was little or no evidence that 74 centromeric cohesin was more depleted than peri-centromeric cohesin (Yokobayashi & 75 Watanabe, 2005). 77Another important meiotic regulatory factor both in fungi and metazoa is a family of 78 proteins related to Spo13 in budding yeast (Wang et al., 1987). These include Moa1 in 79 fission yeast (Yokobayashi & Watanabe, 2005) and Meikin (Kim et al., 2015) in 80 mammals. Though not highly conserved in amino-acid sequences, all members of the 81 family are expressed exclusively during meiosis and have the property of recruiting 82 Polo-like kinases to kinetochores. Because their ablation compromises protection of 83 peri-centromeric cohesion by Shugoshin/Mei-S332 proteins (Katis et al., 2004a;84 Klapholz & Esposito, 1980; Lee et al., 2004; Shonn et al., 2002) and regulation of the 85 anaphase-promoting complex/cyclosome (APC/C) activity (Katis et al., 2004b) as well 86 as co-orientation (Galander et al., 2019; Kim et al., 2015; Matos et al., 2008; Miyazaki 87 et al., 2017), these Spo13-like proteins should be viewed as factors that regulate 88 directly or indirectly numerous...

Kinetochore individualization in meiosis I is required for centromeric cohesin removal in meiosis II

“…7). Our data are in agreement with a recent study, showing that bivalents transferred from meiosis I into meiosis II oocytes behave as if they were in meiosis I and segregated into dyads (Ogushi et al, 2020).…”

“…At this point we ignore its identity, but one attractive candidate is a separate fraction of Rec8, which is distinct from Rec8 on arms and Rec8 protected until anaphase II onset. Indeed, a third fraction of Rec8 has been proposed to exist and to confer loss of sister kinetochore co-orientation and meiosis II cohesin protection upon cleavage by Separase after meiosis I in a very recent study (Ogushi et al, 2020). According to our data, this unknown Separase substrate does not seem to be protected by Sgo2.…”

Separase cleaves the kinetochore protein Meikin to direct the meiosis I/II transition

“…This reduced Plk1 activity leads to a corresponding reduction in pericentromeric Bub1 and Sgo2, allowing for Rec8 phosphorylation and cleavage at anaphase II. This model is consistent with recent findings that Separase activity at meiosis I is required for deprotection of peri-centromeric cohesin (Gryaznova et al, 2020;Ogushi et al, 2020).…”

Kinetochore individualization in meiosis I is required for centromeric cohesin removal in meiosis II

“…Rec8 holding sister chromatids together in metaphase II is localized at the junction of the two sister chromatids between the two CREST dots (see also below and (Lee et al , 2006; Lee et al , 2008; Chambon et al , 2013b; preprint: Ogushi et al , 2020)). It was proposed that bipolar tension moves Sgo2 together with PP2A away from pericentromeric Rec8 for deprotection in metaphase II (Gomez et al , 2007; Lee et al , 2008).…”